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It’s one of the few methods youhave to control theenvironmentoutside amechanicalseal.

API Piping Plan 62:A Reliable Quench System

By Keith Schindler, PE, Schindler Engineering, Inc., and Paul McMahan, Flowserve Corporation

For years, users and manufacturers have attempted to increase mechanical seal reliability. Focus often

has been placed on the seal flush arrangement and methods to control the parameters that affect the seal

environment. Engineering improvements have been made in seal design, face material combinations and

configurations to comply with EPA’s low-emissions regulations and the American Petroleum Institute’s (API)

recommendations. However, little attention has been given to the environment outside the mechanical seal

(atmospheric side) and how this environment affects seal reliability. This article discusses one of the few

methods used to control the environment external to the seal. An appendix beginning on page 28 outlines

guidelines for operation, shutdown and troubleshooting of these systems.

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An external fluid quenchsystem (API Piping Plan62) is designed to im-

merse the outside of a mechani-cal seal assembly and the sec-ondary seals with a clean non-hazardous fluid [1, 2]. This fluidserves multiple purposes.

1) It occludes the atmospherefrom the atmospheric side ofthe mechanical seal assembly,thereby reducing oxidation.

2) Since it is at a slightly higherpressure than atmospheric, itprovides a low flow throughthe area to assist in drainageor removal of product leakageacross the seal faces.

3) Depending on temperatureand solubility of the pump-age in the quench fluid, ithelps to prevent solidificationproduct leakage until suchleakage has exited the closeclearances encountered in thegland. This build-up of prod-uct, if not removed, will oth-erwise accumulate to causethe seal assembly to hang up.

4) For hydrocarbon products ator near their auto-ignitionpoint, the quench fluid coolsthe normal leakage from theseal assembly to a tempera-ture below the product auto-ignition temperature.

When considering an exter-nal fluid quench system, certainrequirements must be incorpo-rated in the design of the seal forthe quench system to be reliable.

� The mechanical seal glandmust be equipped with inletand outlet (drain) quenchconnections. The quenchfluid must drain through theoutlet connection, making itnecessary for the outlet con-nection to be lower than theinlet connection. This ar-rangement will help washaway any product leakage atthe seal faces. The drain con-nection should be located at

the lowest possible point onthe seal gland to prevent adead spot where productleakage can accumulate andaffect seal performance.

� The mechanical seal glandmust be equipped with aclose-clearance throttle bush-ing or other suitable device.Since the quench fluid is fedto the gland under pressure,the pressure forces the fluidout of the gland toward thedriver or bearings through thespace between the shaft andgland ring bore. The close-clearance bushing di-rects thequench flow and any productleakage to the drain instead ofalong the shaft, and reducesthe amount of quench fluidleakage from entering thebearing housing and contam-inating the bearing lubrica-tion. The bushing containsthe quench fluid in the areaof the seal assembly where itis needed, by directing thequench fluid to the atmo-spheric side of the seal assem-bly and the secondary seals.The bushing also acts as anorifice to control the amountof leakage to the atmospherein the event of a catastrophicseal failure.

ApplicationsIn applications such as hot

hydrocarbons and caustics,where oxidation, coking or crys-tal formation (crystallization) is aproblem on the atmospheric sideof the mechanical seal, steam istypically used as the quenchfluid. The steam is introducedinto the inlet quench connectionwhere it is directed around thesealing faces.

The steam quench acts as acoolant for the mechanical seal inhigh temperature applications (>300° F) [2]. The steam coolsthe leakage on the atmosphericside of the sealing faces, whichreduces coke formation and sub-

sequent seal hang-up. For hydro-carbon product streams at ornear their auto-ignition point,the steam helps cool the normalleakage from the seal assemblybelow its auto-ignition tempera-ture. It also reduces cooling ofthe seal faces and the product inviscous or high freezing-point-temperature applications whilethe pump is not running.Damage can occur to the mech-anical seal at start-up, if the prod-uct thickens or freezes at the sealfaces.

For a steam quench applica-tion with enough space in thepump, the mechanical seal glandshould be equipped with an anti-coking baffle [2]. (Figure 1). Theanti-coking baffle routes thesteam to the area of the sealwhere solids collect, then directsthe steam so that it carries thematerial away from the seal andsealing faces to the outlet (drain)connection [2].

The steam quench pressureshould be regulated between 1–3PSIG at the inlet quench connec-tion to prevent any seal prob-lems. Higher-than-recommend-ed steam pressures could affectthe performance of the seal—andwill cause the excess steam toexhaust out of the seal gland.Excess steam will cause moistureto enter the pump bearing hous-ing if the bearing housing is notproperly protected [3].

When steam is used as aquench medium for high-tem-perature applications, it is essen-tial that the steam quench beoperated in a gaseous state andliquid water must not be intro-duced into the gland area. If con-densed steam is introduced to theatmospheric side of the sealassembly, it may result in flashingof the steam in the seal face area,with the consequence of unstablehydraulic forces affecting theatmospheric side of the seal faces.Another possible consequence isdamage to secondary graphitesealing members either throughgalvanic corrosion or damage

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that occurs when the condensa-tion trapped in the secondarysealing member area flashes backto steam.

Figure 2 shows the recom-mended piping system to ensurethat “dry” steam is available as aquench fluid. If the steam supplyline to the equipment is longerthan 25 feet, or is taken from ahigh pressure source where thereis more than a 50-PSI drop

across the controller, reducingthe initial steam pressure to ausable level for the quench, addi-tional measures to prevent con-densation in the steam quenchsystem may be needed. Insu-lation and tracing of the steamsupply system is one option.Others include using the heat ofthe equipment to reheat thesteam quench by wrapping ashort section of tubing around

the equipment, or routing thesteam quench through a waterjacket on the equipment.

In applications where oxida-tion or coking is a problem onthe atmospheric side of themechanical seal and steam is notavailable or can’t be used, nitro-gen is the second most commonquench fluid used (as shown inFigure 3). Similar to the steamquench application, a nitrogenquench is introduced into thequench inlet connection of theseal gland where it is directedunder the sealing faces. Thenitrogen quench purges the oxy-gen from the atmospheric side ofthe seal to reduce oxidation andthe flow of fluid helps removeany build-up from under the sealfaces to prevent seal hang-up.The nitrogen quench also acts asa coolant for the seal in high-temperature applications by cool-ing the leakage on the atmo-spheric side of the sealing faces,which reduces or prevents coke

Figure 1. Mechanical seal with anti-coking baffle

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formation and subsequent sealhang-up in hot services (>300°F)[2]. Since nitrogen is a gas andthe recommended flow rate islow, there is no visible evidenceat the seal gland that the nitrogenquench system is in service [3].The only indication that the sys-tem is working properly is a flowreading from a reliable flowmeter.

The nitrogen quench flowrate should be controlled toapproximately one (1) standardcubic foot per minute (scfm).Higher-than-recommendednitrogen flow rates will not affectthe performance of the seal, butwill substantially increase theoperating cost of the externalquench piping system [3].

Water is a quench fluid usedin sour water, caustic soda andsaltwater brine applications,where the product crystallizes onthe atmospheric side of themechanical seal. The waterquench fluid is introduced intothe inlet quench connection ofthe seal gland where it is directedunder the sealing faces (Figure4). The flow of water washesaway any build-up from underthe sealing faces to prevent sealhang-up.

The quench pressure shouldbe limited to prevent any sealproblems. The flush rate shouldbe controlled so that a slow dripappears at the back side of theseal gland. This should beenough to keep any crystals fromforming under the sealing facesto prevent seal hang-up.

A water quench typicallybecomes a housekeeping prob-lem. The water drips on thepump bracket and the pumpbaseplate, accelerating corrosion[3]. In cold climates, the waterfreezes and becomes a slippinghazard. For this reason, it is com-mon practice to pipe the outletof the drain connection on theseal gland to a suitable drainlocation around the equipment

pad when there is minimal risk ofplugging or fouling of the addi-tional drain piping.

Line-Up & Operating For an external fluid quench

system to be reliable, it must beoperated and maintained proper-ly. This includes establishingclear equipment line-up, operat-ing, preventative maintenance,shutdown and troubleshootingtasks for maintenance and oper-ating personnel. (A detaileddescription of each task is listedin the attached Appendix.)

Remember that the mainisolation valve on an externalfluid quench line should never beopened after the equipment hasbeen prepared for service, orwhile it is in service. The externalfluid quench system should beplaced in service prior to liningup the equipment for opera-tion—and should not be isolateduntil the equipment is removedfor maintenance. Opening thefluid quench line while theequipment is in service (HOT)can seriously damage themechanical seal—and exposeoperating personnel to a serioussafety risk.

ConclusionAn external fluid quench sys-

tem (API Piping Plan-62) canreliably control the environmentoutside a mechanical seal if thesystem is installed and operatedproperly. Designed to immersethe seal faces and the secondaryseals with a clean, non-hazardousfluid, this system will remove anyproduct leakage and build-upfrom the atmospheric side of theseal to prevent seal hang-up, thusextending seal life. Dependingon the product or material beingsealed, the quench system can betailored to fit the application.

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APPENDIX

Equipment Line-Up &Operating Guidelines

The following steps are rec-ommended when putting anexternal fluid quench system(API Plan-62) into service. Thisline-by-line description can beused to assist maintenance andoperating personnel with theirdaily line-up, operating and trou-bleshooting tasks.

1. Open main valve isolating theexternal quench system.

2. Follow the procedure listedbelow for different quenchmediums.a. Steam Quench: (Fig. 2.)

i. Open the drain valve to begin heating up the steam quench line and to remove the conden-sate from the system.

ii. Once the steam quench

piping is HOT and all condensate is out of the system, close drain valve.

iii. Note: � A small amount of condensate may drip from the seal flange. This is normal, but most of it should be removed from the quench system by the steam trap.� Higher steam quench pressure will cause the excess steam to exhaust

from back of seal gland and force condensate to enter bearing housing of the pump or driver.

b. Nitrogen Quench: (Fig. 3.) i. Note:� Throttle needle valve

(or adjust pressure regulator) until flow meter reads one (1) stan-dard cubic foot per minute (scfm). There will be no other visual indicators at the seal

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Figure 2. API Piping Plan-62 Steam Quench Piping Layout

.

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gland to show nitro-gen is flowing. The pres-sure gauge and flow me-ter are the only indica-tors to show the system is operating properly.

� Nitrogen is expensive. Excessive nitrogen flow rates will not damage the mechanical seal or affect its performance, but will increase operating cost of the system [3].

c. Water Quench: (See Fig. 4.)

i. Open needle valve (or block valve upstream of pressure regulator) on quench line near prima-ry seal gland to create recommended flow.

ii. Throttle needle valve (or adjust pressure regu-lator) until a slow water drip appears at back side of seal gland.

� Open needle valve controlling the quenchpressure (or block valve upstream of the pressure

regulator) on quench line near the primary seal gland to create recommended flow. (See Table 1.)

� Proceed with opening all process valves to place the pump in service.

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FFiigguurree 33.. AAPPII PPiippiinngg PPllaann--6622 NNiittrrooggeenn QQuueenncchh PPiippiinngg LLaayyoouutt

WARNING: Never open the main

isolation valve on an external fluid

quench line after the equipment

has been prepared for service or

while it is in service. The external

fluid quench system should be

placed in service prior to lining the

equipment up for operation and

should not be isolated until the

equipment is removed for mainte-

nance. Opening the fluid quench

line while the equipment is in ser-

vice (HOT) can seriously damage

the mechanical seal and places the

operating personnel at a serious

safety risk.

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� Check for leaks aroundany valves and connec-tions in the external fluid quench line.� Start pump per nor-mal start-up procedure.� Once the pump is in service, check the visual indicator (exhausting steam, water dripping and pressure reading) to

ensure the system is per-forming.

Shutdown GuidelinesThe following steps are rec-

ommended to safely isolate anexternal fluid quench system formaintenance.

1. Shut down pump per normalshutdown procedure.

2. Proceed with closing all pro-cess valves to isolate pumpfrom service.

3. Close main valve isolating theexternal fluid quench system.a. Steam Quench: Open

drain valve to remove any condensate from system. This step is important to reduce risk of freezing during cold weather.

b. Nitrogen Quench: No additional steps are required to isolate the system for maintenance.

c. Water Quench: No addi-tional steps are required to isolate the system for maintenance.

4. The equipment is now isolat-ed and ready for mainte-nance.

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FFiigguurree 44.. AAPPII PPiippiinngg PPllaann--6622 WWaatteerr QQuueenncchh PPiippiinngg LLaayyoouutt

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PreventativeMaintenance Tasks

The external fluid quenchsystem should be checked dailyduring normal operator rounds.The Preventative Maintenance(PM) steps outlined below are setup to assist operating personnelin troubleshooting the system.

1. Verify that the main isolationvalve for the external quenchsystem is open.

2. Follow the next steps for thedifferent fluid quench appli-cations.a. Steam Quench:

i. Visually note steam ex-hausting from back of seal gland.

ii. Verify steam trap is operating properly by opening drain valve to see if there is any con-densate in the system.

iii. Visually note reading on pressure gauge. The external steam quench pressure should set between 1–3 PSIG.

iv. Visually note reading on the flow meter (if applicable). It should read between 5 lbs/hr and 10 lbs/hr.

v. Take a temperature reading at the interface of the shaft and sec-ondary sealing device and note the tempera-ture when the steam quench is operating properly. If the temper-ature varies by more than 10° F upon

subsequent inspections, the steam quench sys-tem should be more thoroughly reviewed to ensure it is operating properly.

b. Nitrogen Quench:

i. Visually note reading on flow meter (if appli-cable). The flow meter should read ~ 1 scfm.

ii. Visually note pressure gauge reading. It should be between 1 – 3 PSIG at the inlet connection.

c. Water Quench:

i. Visually note water

dripping from back of the seal gland.

ii. Visually note reading on pressure gauge (if applicable). The exter-nal water quench pres-sure should set be-tween 1 – 3 PSIG at the inlet connection.

Troubleshooting The typical failure mode for

an external fluid quench systemis a closed valve or cloggedquench line. In the event thePreventative Maintenance indi-cators show that the system is notoperating properly, shut down

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Table 1: Recommended flow rates and/or pressures

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the equipment according to thesteps outlined previously.

The tips below are set up toassist operating and maintenancepersonnel in troubleshooting thesystem.

1. Verify that main isolation valvefor the external fluid quenchsystem is open. For an externalsteam quench system, opendrain valve to see if there is ade-quate pressure from the mainisolation valve.

2. Open and close needle valve (or

block valve) to make sure it is

not plugged by debris.

3. If this proves successful, adjustpressure and put equipmentback in service according to theline-up procedure. Otherwise,isolate the equipment and pre-pare to remove external fluidquench line for inspection.

4. Once the equipment is ready formaintenance, remove externalfluid quench line from sealgland.

a. Check needle valve (or pressure regulator) for pluggage.

b. Check main isolation valve for pluggage.

5. If this proves successful:

a. Reconnect external fluid quench piping.

b. Prepare external quenchsystem for service accord-ing to line-up procedure.

6. If the problem can’t be found,contact your Mechanical Sealrepresentative for assistance.

P&S

References1. Dura Seal Manual, The Sealing

Technology Guidebook, Flow-serve Corporation, Copyrighted1994.

2. API-682 Shaft Sealing Systemsfor Centrifugal and RotaryPumps.

3. API Piping Plan, Training Man-ual, Flowserve Corporation,Copyrighted 2000.

Keith D. Schindler is a RotatingEquipment Engineer with SchindlerEngineering, Inc. The firm specializesin machine repair, procedure writing,Root Cause Failure Analysis on prob-lem equipment and operator training.Schindler holds a BS degree inMechanical Engineering from theUniversity of Houston, and is aRegistered Professional Engineer inMichigan and Virginia. Contact himdirectly at SchindlerInc@aol.com

Paul McMahan is the RotatingEquipment Specialist Program Man-ager for Flowserve FSD Seal Groupin the Baton Rouge, LA, ServiceCenter. He has more than 30 years ofexperience with mechanical seals andwas one of the pioneers in themechanical seal alliance concept.McMahan can be reached at pmcma-han@-flowserve.com

A piping plan pocket pal with abrief description of many of the stan-dard API piping plans, includingPlan 62, is available as a downloadin .PDF format or as a handy pocketreference. To obtain your piping planpocket pal, log on to www.Flowserve.-com/seals/literature and request “Me-chanical Seal Piping Plans” publica-tion FRA160.

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